1. Field of the Invention
The present invention relates to an electric double layer capacitor used for various electronic devices, electric devices, and mobile devices.
2. Background Art
An electric double layer capacitor is an element that uses electric energy accumulated in an electric double layer formed on the interface between a polarized electrode and an electrolyte. The electric double layer capacitor can be downsized and can perform charge/discharge of a large capacity. The electric double layer capacitor is thus used widely for backing up a microcomputer, memory or timer, or for assisting various power sources.
FIG. 18 is a sectional view of a conventional electric double layer capacitor. Electric double layer capacitor 41 has a plurality of electrode plates 43, separator 42, and current collecting members 44. Long separator 42 is impregnated with an electrolyte, and is alternately folded in different directions at predetermined lengths like an accordion. Electrode plates 43 are stacked on each other via separator 42 therebetween so that mutually different poles face each other. Flexible current collecting members 44 have substantially the same width as electrode plates 43, are connected to the ends of respective electrode plates 43, and are buried over the whole length of electrode plates 43.
One end of each electrode plate 43 is covered with separator 42 folded like the accordion, and the other end, which is not covered with separator 42, is exposed on a side surface. Current collecting members 44 are led out of the laminated portion of separator 42 at the end on the exposed side. The ends of respective electrode plates 43 are exposed on the alternately opposite side surfaces, so that current collecting members 44 of respective poles are bundled using bundling member 45 whose sectional view is C shape. Bundling members 45 are made of conductive material.
Bundle parts 46 and 47 of collecting members 44 bundled by bundling members 45 are disposed on the outermost sides of different stacking directions of electrode plates 43 for respective poles. In other words, bundle part 46 is disposed on the uppermost side, and bundle part 47 is disposed on the lowermost side. Electric double layer capacitor 41 having this structure is used in a manner that a plurality of electric double layer capacitors 41 are stacked on each other in the stacking direction of electrode plates 43.
As discussed above, in electric double layer capacitor 41, flexible current collecting members 44 connected to the ends of respective electrode plates 43 are led out of the laminated portion of separator 42, and are bundled for the respective poles. Thus, risk of damaging separator 42 when current collecting members 44 are connected to respective electrode plates 43 is not caused, so that electric double layer capacitor 41 can be easily manufactured. A plurality of electric double layer capacitors 41 can be easily connected in series by stacking.
In this structure, however, electric double layer capacitor 41 impregnated with an electrolyte needs to be sealed using a case member made of polytetrafluoroethylene (PTFE) as insulating resin. Additionally, a pair of electrodes cannot extend in the same direction. Therefore, the product size is enlarged, and the cost is high.